In a recent vehicle, when a load is applied from behind the vehicle, a vehicle body rear portion is required to absorb the load. Therefore, a lower structure of the vehicle body rear portion is configured in many cases in such a manner as to be able to absorb a load applied from behind the vehicle by deforming constituent members (such as a rear floor panel, rear side members extending in a front and rear direction of the vehicle on the respective ends of the rear floor panel, and the like) of the lower structure.
For example, Japanese Unexamined Patent Publication No. 2006-205810 and Japanese Unexamined Patent Publication No. 2007-131259 each disclose the following structure. In the structure, rear side members are formed such that a load applied from behind the vehicle can be absorbed in the vehicle body rear portion. Each of the rear side members extends, in front of a spare tire housing, in such a manner as to be inclined upward toward the back of the vehicle. On the vehicle rear side with respect to the inclined portion, each of the rear side members extends horizontally in the front and rear direction of the vehicle. When a load is applied from behind the vehicle, a chevron-like folding (hereinafter, referred to as a “chevron folding”) protruding upward, is formed at an inflection point between the inclined portion and the horizontal portion of each rear side member.
Furthermore, Japanese Unexamined Patent Publication No. 2006-88785 and Japanese Unexamined Patent Publication No. 2006-123708 each disclose the following structure. In the structure, in order for a load applied from behind the vehicle to be absorbed on the rear side of the vehicle body rear portion, the rigidity on the rear side in a lower structure of a vehicle body rear portion is lower than the rigidity on the front side. In particular, the lower structure includes paired rear side members, and a rear cross member which connects front end portions of the paired rear side members. In addition, reinforcing members for joining the rear side members to the rear cross member are provided at left and right corners each formed by a corresponding one of the rear side members and the rear cross member.